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Old 04-18-2008, 03:14 PM   #1
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Default Switching from 20% to 30% fuel?

Very quick thread, Does switching from 20% fuel to 30% fuel make a big difference?

I tried searching and found some info but not quite enough.

I read about some adjustments I might need to do with the HSN and LSN ect...

I also read about "shims" Now what are those? Where do you get them? Give me ALL and ANY info you can about those, ive never heard of them and am interested to learn about em!

Last edited by new to rc cars; 04-18-2008 at 03:41 PM.
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Old 04-18-2008, 03:19 PM   #2
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What engine?????
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Old 04-18-2008, 03:32 PM   #3
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Originally Posted by KThatcher View Post
What engine?????
LRP z.28 spec

It has had 1.5 gallons through it, first was sidewinder 20% for .5 gallons. second was a whole gallon of Nitrotane, cant remember the %. now all my LHS has is 30%.

And I dont race at a track, I race/bash with a friend out in the country.

Thanks.
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Old 04-18-2008, 03:38 PM   #4
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I was wondering the same thing
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Old 04-18-2008, 03:44 PM   #5
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I was wondering the same thing
ok, I found what shims are, dont know why I didnt google it in the first place...

But I still need to know what to change and how to tell if I need more shims or what?

would these fit my engine? (it is not a Novarossi .28 528XR, its a LRP s.28 spec PS)
http://carolinasrc.com/Webstore/Scri...idproduct=2446
http://carolinasrc.com/Webstore/Scri...idproduct=2447

All engines have very thin shims between the cylinder head and the sleeve, and these shims are used to set the clearance between the two parts. You can increase power by removing shims or installing a thinner shim. This will make the combustion chamber smaller and will increase the engine's compression.

To remove the shims, you'll have to remove the cooling head, so take out the screws that hold it in place. You will see the shims on top of the sleeve, or they might be stuck to the head where it meets the sleeve. Remove one shim (if there is more than one) and reinstall the head. Be sure to check the piston/head clearance by manually spinning the crankshaft through one revolution to see whether the piston hits anything. If it does, replace the shim you just removed. The shims are very thin and bend easily, so be careful when you handle them.

Don't do this unless you're an experienced engine tuner. Too much compression and/ or insufficient head clearance may damage your powerplant.
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Old 04-18-2008, 03:56 PM   #6
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What is HSN, and LSN?
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Old 04-18-2008, 04:07 PM   #7
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a .28 engine should already be shimmed for 30% fuel..


you can just switch over without need any more shims.

HSN is high speed needle (main needle)
LSN is low speed needle

you might have to do a slight retune, but overall you'll be gettin more power and cooler temps with the 30 over the 20
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Old 04-18-2008, 04:09 PM   #8
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whatr about an o.s. .12 tg motor, what should I do to switch from 20% to 30% with that motor, btw I use o'donell.
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Old 04-18-2008, 04:16 PM   #9
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Quote:
Originally Posted by imaxx21 View Post
HSN is high speed needle (main needle)
LSN is low speed needle
Okay... got it, thanks!
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Old 04-18-2008, 04:52 PM   #10
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id stay with 20% in a small block personally...
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Old 04-18-2008, 06:15 PM   #11
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Quote:
Originally Posted by imaxx21 View Post
a .28 engine should already be shimmed for 30% fuel..


you can just switch over without need any more shims.

HSN is high speed needle (main needle)
LSN is low speed needle

you might have to do a slight retune, but overall you'll be gettin more power and cooler temps with the 30 over the 20
allright, thats what I like to hear.

Im not sure what shims I have in my engine, its just a stock LRP .28 pullstart edition. I like it because I think its a Truggy engine and I have it in my buggy and it hauls pretty good

I wont know if its running badly or not because im not that experienced yet!! How do you tell if you need more/less shims?

unrelated question: if your engine smokes too much, do you lean it out a little bit?
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Old 04-18-2008, 06:22 PM   #12
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dont worry bout the shims, you're good


smoke is good
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Old 04-18-2008, 07:27 PM   #13
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Yea I just switched from 20 - 30 back to back and it was a noticeable difference in power and I had to fatten it up about 3 hours.
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Old 04-18-2008, 07:36 PM   #14
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Quote:
Originally Posted by imaxx21 View Post
dont worry bout the shims, you're good


smoke is good
How come you wont teach me about shims!! :'(


Quote:
Originally Posted by Furadi View Post
Yea I just switched from 20 - 30 back to back and it was a noticeable difference in power and I had to fatten it up about 3 hours.
good, thats awesome, I didnt think I could get my buggy goin any faster!! damn

you mean "fatten" is richen it up? open the needle? counterclockwise?... just making sure
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Old 04-18-2008, 07:50 PM   #15
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yes fatten = richen = ccw
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